Field of the Invention
The present invention relates to an information processing apparatus, a control method therefor, and a storage medium, and in particular to an information processing apparatus and a control method therefor that are capable of correcting a time-of-day management function in an environment where the time of day cannot be properly measured in the information processing apparatus in a power-saving mode, as well as a storage medium.
Description of the Related Art
For information processing apparatuses (including image forming apparatuses) having a communication function, there is known a technique that, in order to save power, shuts off the power to a network interface card (NIC) and others in the information processing apparatuses in a power-saving mode (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2007-276341). Also, it is known that as a way to save power, a clock gating technique such as reducing the number of clocks of a CPU (central processing unit) in a power-saving mode is used. Power can be saved to a greater extent by using a technique that clock-gates a CPU in a NIC in combination with the technique that shuts off the power to some components and operates an information processing apparatus with only the NIC.
Precisely measuring and managing time-of-day information on an information processing apparatus is a process indispensable for operating systems normally in an information processing apparatus. An information processing apparatus is able to accurately perform processes dependent on the time of day such as automatic execution of a job at a specified time of day and return from a power-saving mode by precisely managing time-of-day information as described above. A CPU and an RTC (real-time clock) are used as means for measuring the time of day in common information processing apparatuses. In general, an RTC works even in a situation where power supply to a system is limited, and is in charge of measuring the time of day in this situation. Accordingly, an RTC is configured to be equipped with a standby power source such as a primary battery. On the other hand, as a way to manage the time of day without using a CPU or an RTC, there is, for example, a technique that obtains time-of-day information from another server on a network by connecting an information processing apparatus to the network (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2003-156579).
However, clock gating of a CPU presents a problem that clock intervals of the CPU become unstable, and a timer of the CPU fluctuates (the timer does not count time with accuracy at regular intervals). In general, an LSI (large-scale integration) comprised of small-scaled circuits such as a NIC has no RTC in many cases, and the time of day cannot be properly measured with an RTC. Namely, in an information processing apparatus that operates with only a NIC in a power-saving mode, if clock gating of a CPU is applied to a small-scale circuit such as a NIC having no RTC, there will arise a problem that the time of day cannot be properly measured. Moreover, even if a NIC has an RTC, the same problem will arise upon battery exhaustion because power is supplied from a primary battery.
Further, in the situation described above, the time of day cannot be properly managed in a power-saving mode, and this presents a problem that processes dependent on the time of day such as automatic execution of a job at a specified time of day and return from the power-saving mode cannot be properly performed.